From DE-OS No. 3 738 924, a spindle featuring splines and a groove is known which is undetachably connected with a crank lever by way of cold working. A disadvantage of this type of connection is that, for achieving the required strength, the material of the lever has to be comparatively thick in order to obtain a sufficient lever abutment surface on the spindle. Further, cold-working the lever requires lever surface treatment after any individual processing operation so as to prevent corrosion. Thus, this known manufacturing method requires a considerable effort and expenditure.
From DE-OS No. 3 643 747 it is further known to manufacture the lever from galvanized deep-drawn sheet metal and to provide for an enlarged abutment surface between lever and spindle in that so-called rim holes are formed by deep drawing. These rim holes are peripheral collar-type rims abutting the spindle with their surface areas which extend along the longitudinal direction of the spindle. In DE-OS No. 3 643 474, the respective rim hole tapers towards its free end and receives a correspondingly conically shaped and splined spindle portion. The end of the spindle which penetrates the rim hole is provided with a thread which allows the spindle to be wedged detachably with the rim hole by means of a securing nut. The processing needed for such a type of connection as well as the number of the necessary individual components impose considerable requirements.
Thus, the present invention includes a gear part which features a particularly simple design and suggests a durable connection between the crank lever and the spindle.
This invention solves its object by making use of the accessibility of the outer surface area of the rim hole so that the rim hole can be connected durably with the spindle in a simple manner. In this way it is possible to connect the lever of deep-drawn sheet metal undetachably and in an inexpensive manner with the spindle, yet also with any other component such as with a stud or ball pin. The principle of this connection type consists in that, after the insertion of the spindle, projections will be molded into the rim hole from its outer surface area which will project into corresponding recesses within the spindle, thus securing the same in relation to the lever. Preferably, the recess may be a peripheral groove engaged by individual projections of the rim hole or, also, by a peripheral projection of the rim hole.
In order to achieve a particularly good fixation against axial twisting, forces are applied to the outer surface area of the rim hole thereby pressing the inside surface area of the rim hole into the splines. By pressing the spindle into the collar and thus causing the collar to widen, such a technique is particularly advantageous for deep drawing. In this case a reduced deformation will keep the opening width of the rim hole smaller than the diameter of the spindle which will then be pressed into the opening, thus the splines of the spindle cutting into the inside surface area of the rim hole.
It is easy to see that using galvanized deep-drawn sheet metal as a rule will be less expensive than the use of compact steel components whose surfaces will require additional finishing and refinement after the individual processing operations. It is a special feature of the zinc which coats the sheet steel that, in the process of the deformation and punching operations, the zinc will smear over the newly formed surface and thus in a simple manner provides for a durable rust protection. Preferably, lever areas are punched out which are not necessary for the strength behaviour of the lever. These areas can be enlarged in particular by reinforcing the strength of the lever by means of stiffening corrugations. Punching the clearances out will on the one hand produce a saving in terms of material and, hence, in terms of weight without the lever, as already described further above, having to be protected against corrosion by means of separate measures.
A further advantage results in that, the flux of force between the spindle and the lever is spread over the entire circumference of the rim hole. Amongst other things, this results from the increased elasticity of the lever. A further possibility of reinforcing the area of connection between lever and spindle results from constructing, at least in the area of connection of the spindle and/or stud, the crank lever from of two superimposed coats of galvanized sheet steel which are formed by folding. This allows to increase the material thickness of the lever locally, yet simultaneously not excluding the deep-drawn molding of rim holes.
Any expert will easily realize that the possibility of connection described for the spindle in relation to the lever will also apply to other components such as studs or ball pins, pins and the like. This invention is thus not restricted to the application of this connection between spindle and lever.
Manufacturing the rim holes and/or stiffening corrugations is made particularly easy by pointing the stiffening corrugation in the same direction. In this case, it is possible to reduce the number of the operations and of the tools used.